At present, there are different patents disclosing devices that measure shots in weapons, such as patent document ES2292842(T3), which describes a shot counting device based on counting the number of shells expelled out of a firearm chamber through an expulsion window, and showing on a display screen the number of shots that therefore remain available in the loader mounted on the weapon. This shot counter has the limitation of only showing the information regarding the number of actual shots, as it is possible to lose cartridges through the chamber when it is mounted, or because there is a discharge without detonation following the firing of defective cartridges, measuring only the number of undetonated shells and cartridges that are expelled by the chamber. This patent moreover does not possess a method to ratify whether or not a shot was fired.